The present invention relates to electrostatic treatment of fluid systems and more particularly to the construction and operation treating devices having electrostatic fields.
Apparatus for the treatment of moving liquid by causing electric current flow or discharge therein and/or impressing electrically induced fields thereacross have been known for many years, but the application of such devices to common industrial and domestic problems, such as water system scaling and clogging, has met with varying success. Some installations have appeared to be functional while others which seemed to be operating under generally similar circumstances obviously failed and no broadly accepted reasons for the different results have been advanced. The optimum type, size and characteristics of a treater to produce desired and reliable results in a particular environment appear to have been unnecessarily limited with respect to DC voltage imposed on the electrostatic field. A predictive method is disclosed in U.S. Pat. No. 4,073,712 wherein a positively charged axially placed conduit electrode insulated by a dielectric material provides an electrostatic field through flowing water in the conduit whereabout the conduit has a negatively charged electrode, thereby providing a three capacitor system.
A large number of factors and complex interactions are apparently involved in the treating process. This seems logical since such liquid systems are themselves usually highly complex, including variations in dissolved salts, suspended solids, turbulence, pH, piping, electrical environment, temperature, pressure, etc. Many liquid clogging mechanisms, including water system scaling, involve the electrostatic relations between suspended particles, the carrier liquid and the walls of the piping network. Thus, an electrostatic field effectively developed across a section of flowing water primarily affects not only the water, but mainly suspended, especially colloidal size, particles immersed in the water. The effect of the field will depend, in large measure, upon the relationship of the natural electrostatic charge on such immersed particles to the electrostatic charge on the various surfaces of the treater and how the latter charge induces a response on the liquid contacting surfaces of the piping network. If relative conditions are proper, the particles will be urged by the field to remain in suspension or migrate toward a charged electrode isolated from the walls of the piping network, thus reducing the tendency to form flow restricting deposits. The reduction of colloid particles which are capable of acting as seeds for nucleation of scale building crystal formations results in reduced tendency for scale deposition.
The natural electrostatic charge on the immersed particles in the liquid, or more accurately, the overall charge effect of the various groups of particles normally associated in the same system, can be determined by known procedures, but the control of the electrostatic charge on critical treater surfaces has been heretofore very limited due to configuration of the electrodes. The present invention reverses a decades old method of fabricating conduit electrostatic field treatment devices such that the positive, ground electrode is situated generally within the axial space of the conduit, whereabout are situated dielectric insulated negatively charged electrode(s) such that the liquid flowing in the conduit becomes negatively charged for later process advantage.
The electrostatic field between particular water treater surfaces, in large part, can be predicted and controlled by limiting certain parameters in treater construction and installation, especially the dielectric constant of the insulating material or materials in contact with the water, the efficiency of the insulating material or materials and seals in preventing charge leakage, and the physical size ratio of the treater parts which form the surfaces producing the electrostatic field across the water complex under treatment. The word xe2x80x9cwaterxe2x80x9d, as used herein, means water complexes containing dissolved and suspended solids, etc., as are normally found in a great many industrial and domestic applications. Of more importance, however, is to provide a method whereby high DC voltages may be effectively developed across the flowing fluids.
The manipulation of electrical potentials, to produce relationships within certain parameters calculated from an equation which presents a mathematical model of the treater as three capacitors connected in series, results in operable treaters, while devices having relationships falling outside those parameters are apparently less-functional or only marginal in operation. The parameters of those variables are described with reference to a specific example below.
The principal objects of the present invention are: to provide operable and efficient electrostatic water treaters; to provide such treaters which function to predictably inhibit the formation of scale from colloidal particles immersed in flowing water; to provide a treater construction which substantially reduces the formation of scale in piping systems and may function to remove scale already formed; to provide a method of designing operable and efficient electrostatic treaters for particular installations; to provide a method of treating water to reliably inhibit the formation of certain clogging deposits in the piping system containing same; to provide a dependable alternative to many types of chemical water treatment; and to provide such methods and apparatus which have wide application in improving desired properties of water for industrial and domestic purposes at minimal cost and maximum safety.
In U.S. Pat. No. 4,886,593, the disclosure explains that xe2x80x9cThe present invention is based on the discovery that the application of an electrostatic field to water of a sufficient intensity is such as to kill or inhibit the growth of bacteria or other microorganisms.xe2x80x9d (col. 1, lines 41-44). The sufficiency of the field intensity is pointed out to be xe2x80x9cvery high voltages are being utilized with the present inventionxe2x80x9d (col. 3, lines 13-14) at a maximum of xe2x80x9ca high voltage DC current of the order 5,000 volts or upward to provide an electrostatic field in the water.xe2x80x9d (col. 4, lines 13-14). Just what is meant by xe2x80x9cof the order 5,000 volts or upwardsxe2x80x9d is evident from two specific examples. A specific example in column 4, lines 23-26, says that the maximum voltage is xe2x80x9c5000 DCxe2x80x9d. The only other specific example in column 5, lines 56-60, says that the maximum applied voltage is xe2x80x9c6,500 volts D.C.xe2x80x9d. That example discloses a Variac controller to assure that applied voltage could not exceed xe2x80x9cof the order 5,000 volts or upwardsxe2x80x9d, i.e., as high as xe2x80x9c6,500 volts D.C.xe2x80x9d. That no substantially higher voltage was contemplated is evident from claim 11, wherein the current is xe2x80x9cin magnitude insufficient to present any danger to human lifexe2x80x9d (col. 7, lines 17-19). The tubular member 7 is merely a waterproof sleeve of polypropylene or an xe2x80x9celectrically insulating materialxe2x80x99 (col. 5, lines 8-9). The skilled person understands from this lack of disclosure that Gibbs teaches that at the voltage range of up to 6,700 volts DC that a bacteria-killing electrode may be killed with milliamp current. No further teaching is disclosed as to any other beneficial effect of changing the type of material or thickness of material used in the tubular member 7. It is not conceivable that the skilled person even perceives an invitation to try voltages above 10,000 volts DC applied between the electrode and the pipe wall as being potentially dangerous to humans. In addition, as disclosed below and as disclosed in U.S. Pat. No. 5,591,317, higher applied voltage to the disclosed material of tubular member 7 will cause the electrode to burn through the tubular member and self-destruct and/or be ineffective.
It is quite clear what expectations the skilled person has for Teflon wrapped electrodes in light of the disclosure of U.S. Pat. No. 5,591,317 that:
xe2x80x9cThis commercial generator consists of a Teflon wrapped metallic tube and operates at about 10,000 volts. The deposit formation was found to be approximately seven times larger with the prior art equipment than with the device of the invention. Moreover, the prior art equipment did not show any significant improvement over the rate of scaling of untreated water, supporting the hypothesis that higher operating voltages are required for large-scale industrial applications. Most importantly, though, when attempts were made to operate prior-art equipment at higher voltages in water of comparable quality, again no visible effects were noted.xe2x80x9d (col. 8, lines 48-59)
This patent unequivocally denies any effectiveness of Teflon wrapped electrodes at voltages of 10,000 volts DC and above. This skilled person has no expectations other than abject failure for applying Teflon or any other polymer to an electrode to generate sufficient dielectric strength to induce an effective de-scaling field. U.S. Pat. No. 5,591,317 continues:
xe2x80x9c. . . the Teflon layer had to be increased substantially in order to withstand the higher voltage (either by using two layers of Teflon heat shrunk around the metallic electrode or by increasing the thickness of a single layer). Because of the relatively low dielectric coefficient of Teflon in comparison to ceramics (2.1 versus about 9.4), a thicker layer of Teflon produces a greatly reduced electric field across the water body, such that particle charge is not induced even at higher operating voltages.xe2x80x9d (col. 8, lines 63-67 and col. 9, lines 1-5)
and
xe2x80x9cAnother problem is related to the thickness of the dielectric material utilized in the prior art. In order to optimize its capacitance, the layer of Teflon used to coat the positive electrode is kept to a minimum (Means et al. disclose five to twenty-five thousands (sic) of an inch as the preferred thickness). This causes the dielectric layer to be more vulnerable to imperfections of construction that might cause arcing or other operating stresses that could result in interruption of insulation. As a result of these constraints, the devices of the prior art are not suitable at voltages higher than 10,000 volts, beyond which they quickly experience breakdowns.xe2x80x9d(col. 3, lines 22-38)
Every reference by U.S. Pat. No. 5,591,317 to a Teflon coated electrode warns the skilled person away from it""s use for voltages above 10,000 volts DC.
U.S. Pat. No. 5,681,457 shows an xe2x80x9cinsulating layerxe2x80x9d identical in function to the xe2x80x9ctubular memberxe2x80x9d of U.S. Pat. No. 4,886,593 in low voltage applications. Both say that this layer next to the conductor can be polyethylene, but that its only function is to keep the water off of the conductor.
The present invention comprises an insertion type electrode adapted to operate at modulated high voltages by use of a thin layer polymer as a dielectric.